no apple snails are on the same boat as the guppies, it is a matter of the betta's personality. I personally have had much success with the guppies, but then again i have a never ending supply in the form of a breeding tank. Out of the 7 betta that i have cared for, only one attacked guppies, he attacked the short finned males which i thought was odd... So simply put, the on;y way to know is to try it. Guppies want a little space an a few friends, like any schooling fish, if you call what they do schooling. And the betta needs room too. I care for a ten gallon at a cousin's house that does have bettas and guppies, fancy ones at that. The two never bother one another. So it is doable, I make her do more water changes though to keep up with the bioload. Sorry for the blabbing, I breed guppies and love bettas, so i had to say my mind.